unit suffix for zero values is necessary for no reason

[GoogleCodeExporter]

.foo{
  margin:0;
  padding:0;
  position: fixed;
  left:0;
  top:0;
}

this code is valid because the value 0 doesn't require a unit. even through, it 
gets converted as:

.foo { position: fixed; }

Original issue reported on code.google.com by imnother...@gmail.com on 18 Apr 2012 at 9:22